package testsql;

import java.util.ArrayList;
import java.util.List;

public class Q403 {

	public static void main(String[] args) {
		Solution solution = new Q403.Solution();
		int[] candidates = new int[]{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,
				16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,
				36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,
				57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,
				78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,
				100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,
				116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,
				132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,
				148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,
				165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,
				182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,198,
				199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,216,
				217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,234,
				235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,252,
				253,254,255,256,257,258,259,260,261,262,263,264,265,266,267,268,269,270,271,
				272,273,274,275,276,277,278,279,280,281,282,283,284,285,286,287,288,289,290,
				291,292,293,294,295,296,297,298,299,300,301,302,303,304,305,306,307,308,309,
				310,311,312,313,314,315,316,317,318,319,320,321,322,323,324,325,326,327,328,
				329,330,331,332,333,334,335,336,337,338,339,340,341,342,343,344,345,346,347,
				348,349,350,351,352,353,354,355,356,357,358,359,360,361,362,363,364,365,366,
				367,368,369,370,371,372,373,374,375,376,377,378,379,380,381,382,383,384,385,
				386,387,388,389,390,391,392,393,394,395,396,397,398,399,400,401,402,403,404,
				405,406,407,408,409,410,411,412,413,414,415,416,417,418,419,420,421,422,423,
				424,425,426,427,428,429,430,431,432,433,434,435,436,437,438,439,440,441,442,443,
				444,445,446,447,448,449,450,451,452,453,454,455,456,457,458,459,460,461,462,463,
				464,465,466,467,468,469,470,471,472,473,474,475,476,477,478,479,480,481,482,483,
				484,485,486,487,488,489,490,491,492,493,494,495,496,497,498,499,500,501,502,503,
				504,505,506,507,508,509,510,511,512,513,514,515,516,517,518,519,520,521,522,523,
				524,525,526,527,528,529,530,531,532,533,534,535,536,537,538,539,540,541,542,543,
				544,545,546,547,548,549,550,551,552,553,554,555,556,557,558,559,560,561,562,563,
				564,565,566,567,568,569,570,571,572,573,574,575,576,577,578,579,580,581,582,583,
				584,585,586,587,588,589,590,591,592,593,594,595,596,597,598,599,600,601,602,603,
				604,605,606,607,608,609,610,611,612,613,614,615,616,617,618,619,620,621,622,623,
				624,625,626,627,628,629,630,631,632,633,634,635,636,637,638,639,640,641,642,643,
				644,645,646,647,648,649,650,651,652,653,654,655,656,657,658,659,660,661,662,663,
				664,665,666,667,668,669,670,671,672,673,674,675,676,677,678,679,680,681,682,683,
				684,685,686,687,688,689,690,691,692,693,694,695,696,697,698,699,700,701,702,703,
				704,705,706,707,708,709,710,711,712,713,714,715,716,717,718,719,720,721,722,723,
				724,725,726,727,728,729,730,731,732,733,734,735,736,737,738,739,740,741,742,743,
				744,745,746,747,748,749,750,751,752,753,754,755,756,757,758,759,760,761,762,763,
				764,765,766,767,768,769,770,771,772,773,774,775,776,777,778,779,780,781,782,783,
				784,785,786,787,788,789,790,791,792,793,794,795,796,797,798,799,800,801,802,803,
				804,805,806,807,808,809,810,811,812,813,814,815,816,817,818,819,820,821,822,823,
				824,825,826,827,828,829,830,831,832,833,834,835,836,837,838,839,840,841,842,843,
				844,845,846,847,848,849,850,851,852,853,854,855,856,857,858,859,860,861,862,863,
				864,865,866,867,868,869,870,871,872,873,874,875,876,877,878,879,880,881,882,883,
				884,885,886,887,888,889,890,891,892,893,894,895,896,897,898,899,900,901,902,903,
				904,905,906,907,908,909,910,911,912,913,914,915,916,917,918,919,920,921,922,923,
				924,925,926,927,928,929,930,931,932,933,934,935,936,937,938,939,940,941,942,943,
				944,945,946,947,948,949,950,951,952,953,954,955,956,957,958,959,960,961,962,963,
				964,965,966,967,968,969,970,971,972,973,974,975,976,977,978,979,980,981,982,983,
				984,985,986,987,988,989,990,991,992,993,994,995,996,997,998,999};
//		int[] candidates = new int[]{0,2,4};
		System.out.println(solution. canCross(candidates));
	}
	
	public static class Solution {
	    public boolean canCross(int[] stones) {
	        List<List<Integer>> moveSteps = new ArrayList<>();
	        boolean[] f = new boolean[stones.length];
	        moveSteps.add(new ArrayList<Integer>());
	        List<Integer> step1 = new ArrayList<Integer>();
	        step1.add(1);
	        moveSteps.add(step1);
	        f[1] = true;
	        if(stones[0] != 0 || stones[1] != 1){
	            return false;
	        }
	        for(int i=2; i<stones.length; i++){
	            List<Integer> moveStep = new ArrayList<>();
	            for(int j=i-1; j>=1; j--){
	                if(f[j]){
	                    List<Integer> lastMoveStep = moveSteps.get(j);
	                    for(Integer step : lastMoveStep){
	                        if(stones[i]-stones[j] == step-1){
	                            moveStep.add(step-1);
	                            f[i] = true;
	                            break;
	                        }
	                        if(stones[i]-stones[j] == step){
	                            moveStep.add(step);
	                            f[i] = true;
	                            break;
	                        }
	                        if(stones[i]-stones[j] == step+1){
	                            moveStep.add(step+1);
	                            f[i] = true;
	                        }
	                    }
	                }
	            }
	            moveSteps.add(moveStep);
	        }
	        return f[stones.length-1];
	    }
	}

}
